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Conceptual questions

What three factors affect the heat transfer that is necessary to change an object’s temperature?

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The brakes in a car increase in temperature by Δ T size 12{ΔT} {} when bringing the car to rest from a speed v size 12{v} {} . How much greater would Δ T size 12{ΔT} {} be if the car initially had twice the speed? You may assume the car to stop sufficiently fast so that no heat transfers out of the brakes.

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Problems&Exercises

On a hot day, the temperature of an 80,000-L swimming pool increases by 1 . 50ºC size 12{1 "." "50"°C} {} . What is the net heat transfer during this heating? Ignore any complications, such as loss of water by evaporation.

5 . 02 × 10 8 J size 12{5 "." "02" times "10" rSup { size 8{8} } `J} {}

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Show that 1 cal/g ºC = 1 kcal/kg ºC size 12{1`"cal/g" cdot °C=1`"kcal/kg" cdot °C} {} .

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To sterilize a 50.0-g glass baby bottle, we must raise its temperature from 22 . 0 ºC to 95 . C . How much heat transfer is required?

3. 07 × 10 3 J

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The same heat transfer into identical masses of different substances produces different temperature changes. Calculate the final temperature when 1.00 kcal of heat transfers into 1.00 kg of the following, originally at 20 . C : (a) water; (b) concrete; (c) steel; and (d) mercury.

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Rubbing your hands together warms them by converting work into thermal energy. If a woman rubs her hands back and forth for a total of 20 rubs, at a distance of 7.50 cm per rub, and with an average frictional force of 40.0 N, what is the temperature increase? The mass of tissues warmed is only 0.100 kg, mostly in the palms and fingers.

0 . 171º C size 12{0 "." "171"°C} {}

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A 0.250-kg block of a pure material is heated from 20 . C size 12{"20" "." 0°C} {} to 65 . C size 12{"65" "." 0°C} {} by the addition of 4.35 kJ of energy. Calculate its specific heat and identify the substance of which it is most likely composed.

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Suppose identical amounts of heat transfer into different masses of copper and water, causing identical changes in temperature. What is the ratio of the mass of copper to water?

10.8

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(a) The number of kilocalories in food is determined by calorimetry techniques in which the food is burned and the amount of heat transfer is measured. How many kilocalories per gram are there in a 5.00-g peanut if the energy from burning it is transferred to 0.500 kg of water held in a 0.100-kg aluminum cup, causing a 54 . C temperature increase? (b) Compare your answer to labeling information found on a package of peanuts and comment on whether the values are consistent.

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Following vigorous exercise, the body temperature of an 80.0-kg person is 40 . C . At what rate in watts must the person transfer thermal energy to reduce the the body temperature to 37 . C in 30.0 min, assuming the body continues to produce energy at the rate of 150 W? 1 watt = 1 joule/second or 1 W = 1 J/s .

617 W

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Even when shut down after a period of normal use, a large commercial nuclear reactor transfers thermal energy at the rate of 150 MW by the radioactive decay of fission products. This heat transfer causes a rapid increase in temperature if the cooling system fails ( 1 watt = 1 joule/second or 1 W = 1 J/s and 1 MW = 1 megawatt ) . (a) Calculate the rate of temperature increase in degrees Celsius per second ( ºC/s ) if the mass of the reactor core is 1 . 60 × 10 5 kg and it has an average specific heat of 0.3349 kJ/kgº C . (b) How long would it take to obtain a temperature increase of 2000º C , which could cause some metals holding the radioactive materials to melt? (The initial rate of temperature increase would be greater than that calculated here because the heat transfer is concentrated in a smaller mass. Later, however, the temperature increase would slow down because the 5 × 10 5 -kg steel containment vessel would also begin to heat up.)

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The figure shows a view from above of a radioactive spent fuel pool inside a nuclear power plant.
Radioactive spent-fuel pool at a nuclear power plant. Spent fuel stays hot for a long time. (credit: U.S. Department of Energy)

Questions & Answers

A golfer on a fairway is 70 m away from the green, which sits below the level of the fairway by 20 m. If the golfer hits the ball at an angle of 40° with an initial speed of 20 m/s, how close to the green does she come?
Aislinn Reply
cm
tijani
what is titration
John Reply
what is physics
Siyaka Reply
A mouse of mass 200 g falls 100 m down a vertical mine shaft and lands at the bottom with a speed of 8.0 m/s. During its fall, how much work is done on the mouse by air resistance
Jude Reply
Can you compute that for me. Ty
Jude
what is the dimension formula of energy?
David Reply
what is viscosity?
David
what is inorganic
emma Reply
what is chemistry
Youesf Reply
what is inorganic
emma
Chemistry is a branch of science that deals with the study of matter,it composition,it structure and the changes it undergoes
Adjei
please, I'm a physics student and I need help in physics
Adjanou
chemistry could also be understood like the sexual attraction/repulsion of the male and female elements. the reaction varies depending on the energy differences of each given gender. + masculine -female.
Pedro
A ball is thrown straight up.it passes a 2.0m high window 7.50 m off the ground on it path up and takes 1.30 s to go past the window.what was the ball initial velocity
Krampah Reply
2. A sled plus passenger with total mass 50 kg is pulled 20 m across the snow (0.20) at constant velocity by a force directed 25° above the horizontal. Calculate (a) the work of the applied force, (b) the work of friction, and (c) the total work.
Sahid Reply
you have been hired as an espert witness in a court case involving an automobile accident. the accident involved car A of mass 1500kg which crashed into stationary car B of mass 1100kg. the driver of car A applied his brakes 15 m before he skidded and crashed into car B. after the collision, car A s
Samuel Reply
can someone explain to me, an ignorant high school student, why the trend of the graph doesn't follow the fact that the higher frequency a sound wave is, the more power it is, hence, making me think the phons output would follow this general trend?
Joseph Reply
Nevermind i just realied that the graph is the phons output for a person with normal hearing and not just the phons output of the sound waves power, I should read the entire thing next time
Joseph
Follow up question, does anyone know where I can find a graph that accuretly depicts the actual relative "power" output of sound over its frequency instead of just humans hearing
Joseph
"Generation of electrical energy from sound energy | IEEE Conference Publication | IEEE Xplore" ***ieeexplore.ieee.org/document/7150687?reload=true
Ryan
what's motion
Maurice Reply
what are the types of wave
Maurice
answer
Magreth
progressive wave
Magreth
hello friend how are you
Muhammad Reply
fine, how about you?
Mohammed
hi
Mujahid
A string is 3.00 m long with a mass of 5.00 g. The string is held taut with a tension of 500.00 N applied to the string. A pulse is sent down the string. How long does it take the pulse to travel the 3.00 m of the string?
yasuo Reply
Who can show me the full solution in this problem?
Reofrir Reply
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Source:  OpenStax, College physics for ap® courses. OpenStax CNX. Nov 04, 2016 Download for free at https://legacy.cnx.org/content/col11844/1.14
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